Dump trucks include an articulated dump body, or dump bin, which is moved between a down position and an up position to provide for the transportation of a material from one location to another. The transported material can include a fluid, a solid material, and aggregates of the same material or different materials. Most generally aggregates of materials are transported in a dump truck, since the aggregates tend to flow relatively easily from the articulated bin when one end is elevated with respect to another end. The articulated bin typically includes bin lift cylinders positioned such that the force exerted by the cylinders moves the bin from a generally horizontal position to an inclined position with respect to the horizontal position. Other dump truck designs use multi-stage lift cylinders to take advantage of the fact that decreasing force is required as lift increases. A multi-stage cylinder at an initial extension provides a high force at low speed. As the cylinder extension continues and the additional stages are activated, speed increases and force decreases. Thus, faster bin raise times are realized.
In one embodiment of a known dump truck, the dump bin is inclined during movement of the bin with respect to a frame of the vehicle. The bin is moved from a relatively horizontal position (negative three degrees in one embodiment with respect to the frame) to a maximum tipping angle of approximately seventy degrees with respect to the frame during the bin dumping operation.
In these and other types of dump trucks, the dump bin position relative to the vehicle frame is measured using a rotary sensor. In one embodiment, the rotary sensor is a rotary Hall-effect sensor. To determine the relative position of the dump body with respect to the vehicle frame, a vehicle control unit, or electronic control unit, records the sensor output values at two specific points along the sensor range—a dump bin up position and a dump bin down position. The measured up value and the measured down value determine a resulting electrical range which can be used in determining the dump bin position between generally horizontal position and the maximum inclined position. This process requires an operator to verify the dump bin is positioned at a maximum downward position or at a maximum upward position. External forces acting on the system can lead to a shift in the values defining the electrical range which, in turn, defines the dump bin position. The dump bin position, as interpreted by the vehicle control unit, can consequently be inaccurate or incorrect, which necessitates a recalibration by a vehicle technician.
What is needed therefore is a dump bin position sensor system with provides an accurate calibration or recalibration procedure which is made without significant operator or technician intervention.